The present invention relates to a series of perhydrothiazepine derivatives which have the valuable ability to lower blood pressure and hence which are of potential use in the treatment of humans and other animals suffering from elevated blood pressure.
There is considerable evidence that reduction of elevated blood pressure reduces the risk of morbidity and mortality. Elevated blood pressure (hypertension) can be caused by a variety of factors and a large number of drugs is available for the treatment of hypertension, the drug of choice being dictated in large measure by the cause of the hypertension, as well as the degree of hypertension and the acceptance of the treatment by the patient. One of the known causes of hypertension is the presence in blood plasma of the polypeptide known as angiotensin II, and a reduction in the blood plasma levels of angiotensin II has been shown to reduce hypertension. The first step in the production of angiotensin II in the mammalian body is the conversion of a blood protein, by the enzyme renin to a polypeptide known as "angiotensin I". This angiotensin I is then converted by angiotensin converting enzyme (hereinafter referred to, as is conventional, as "ACE") to angiotensin II. Clearly, this preparative route provides several opportunities for reducing the plasma levels of angiotensin II, for example by inhibiting the activity of renin or of ACE. Certain polypeptides have been found to inhibit the activity of renin and have been proposed for use as hypotensive agents. Recently, it has also been discovered that certain perhydrothiazepine compounds are capable of inhibiting the activity of ACE and similarly have been proposed for use as hypotensive agents.
An advantage of inhibiting the activity of ACE, as compared with inhibiting the activity of renin, is that ACE not only participates in the formation of angiotensin II, but also participates in the metabolism of bradykinin, converting it to an inert substance. Bradykinin is a natural vasodilator and its elimination would thus be a further positive factor in elevated blood pressure.
For example, certain perhydro-1,4-thiazepin-5-one derivatives (as well as their corresponding thiazocine analogs) are disclosed in European Patent Publication No. 68,173; these thiazepine derivatives differ from those of the present invention principally in being unsubstituted at the 2- and 3-positions. There is also a mention of certain 1,4-thiazepine derivatives similar to those of the present invention in European Patent Publication No. 120,728 (published after the priority dates of the present application), but the 1,4-thiazepine derivatives disclosed therein differ from those of the present invention primarily in the nature of the substituent at the 6-position; additionally, those derivatives actually disclosed are unsubstituted at both the 2- and 3-positions.
The compounds of the present invention have the advantage over the prior art compounds of higher activity and a longer duration of activity, in general, than the prior art compounds, especially those of European Patent Publication No. 68,173. The compounds of the invention differ from the prior art compounds in that they possess at the 2- and/or 3-positions a group selected from certain specific groups which have an essentially hydrophobic (or lyophilic) nature. It is believed that the hydrophobic nature of such groups leads to enhanced binding of the compound to ACE (hence inhibiting the activity of ACE to a greater degree) and an increase in fat-solubility (which leads to enhanced retention in the tissues of the mammalian body and delayed excretion). These factors together lead to the expectation that the compounds of the invention will demonstrate a greater ability to lower blood pressure, coupled with a greater duration of activity.
The compounds of the invention are named herein as perhydro-1,4-thiazepine derivatives; an alternative nomenclature sometimes employed is as 1-thia-4-azacycloheptane derivatives.